The white stretch Lincoln was headed across San Francisco Bay, carrying the bride-to-be and eight of her friends for a bachelorette party.

Five of them, including the bride, never made it across.

Somewhere on the seven-mile San Mateo-Hayward bridge, the limousine caught fire. The driver and four members of the bachelorette party got out, but the bride -- identified by a relative as 31-year-old Neriza Fojas -- and four others died in the burning limo Saturday night, the California Highway Patrol said.

"The flames were gigantic," said Roxanne Guzman, who was crossing the bridge with her husband and brother about 10 p.m. Saturday (1 a.m. Sunday ET). "The flames were so big and radiating so much heat that I could feel the heat off of my face, and I was in my car the entire time."

Guzman said the survivors appeared to be in a state of shock on the shoulder of the roadway, with three of them crying. Other passersby had stopped, but police and firefighters hadn't arrived yet, she said.

The driver was uninjured, but the four surviving women were treated for smoke inhalation, California Highway Patrol spokesman Ron Simmons said Sunday. The cause of the blaze was under investigation.

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"Looking at the photos, it appears it started in the trunk," Simmons said. "But at this time, we don't know officially if the fire started inside the vehicle or on the exterior."

Lovela Nicolas, the sister-in-law of Fojas' sister, said Fojas was a registered nurse. The Fresno woman was slated to be married in June, and she and her friends had hired the Lincoln for her bachelorette party, Nicolas said.

"Neriza was getting married, going to Philippines to get married there and have ceremony there and the reception," Nicolas told CNN from her home in Honolulu.

The mother of one of the surviving women told CNN affiliate KTVU that her daughter, Mary Guardiano, was upset but physically OK.

"She's very sad. She is crying," said Rosita Guardiano.

In a written statement, the limousine company said it was "deeply saddened" by the deaths.

"LimoStop Inc. will do everything possible to investigate and assist authorities in determining the cause of this fire in order to help bring forth answers and provide closure to the victims and their families," it said.

Medical examiners may need up to two days to identify the remains, San Mateo County Deputy Coroner Roger Fielding said.